Coil assembly for moving-coil instruments

ABSTRACT

A coil assembly for moving-coil instruments wherein the coil is wound around a hollow rectangular frame connected with two elastic plastic carriers each of which supports a staff. The carriers are adjacent to two outer sides of the frame which are located opposite each other, and each carrier is normally separated from the adjoining portion of the coil by a gap so that it can be flexed inwardly in response to axial pressure against the respective staff. At least one of the carriers supports a holder for the pointer, balance weight and/or other parts of the coil assembly.

United States Patent COIL ASSEMBLY FOR MOVING-COIL INSTRUMENTS 18 Claims, 4 Drawing Figs.

Appl. No. Filed Patented Assignee Priority us. Cl 324/154, 324/125 rm. Cl G0lr 1/00, GOlr 1/14 Field of Search 324/125,

Primary ExaminerAlfred E Smith AttorneyMichael S. Striker ABSTRACT: A coil assembly for moving-coil instruments wherein the coil is wound around a hollow rectangular frame connected with two elastic plastic carriers each of which supports a staff. The carriers are adjacent to two outer sides of the frame which are located opposite each other, and each carrier is normally separated from the adjoining portion of the coil by a gap so that it can be flexed inwardly in response to axial pressure against the respective stafi At least one of the carriers supports a holder for the pointer, balance weight and/or other parts of the coil assembly.

PATENTEDOBT 19 I911 3,614.61 2

INVENTOR. wlLLy mgsewmu FRITZ RUMPELEIN BY FRANZ LANDBRECHT PAUL KOPF mw/m M1,,

COIL ASSEMBLY FOR MOVING-COIL INSTRUMENTS BACKGROUND OF THE INVENTION The present invention relates to moving-coil instruments in general, and more particularly to improvements in coil assemblies of such instruments. Still more particularly, the invention relates to improvements in the manner of connecting the parts of moving coil assemblies to each other and of selecting the material, configuration and other characteristics of such parts.

SUMMARY OF THE INVENTION An object of the invention is to provide a coil assembly which is cheaper, more rugged and simpler than presently known coil assemblies.

Another object of the invention is to provide a coil assembly which can be used with particular advantage in tape recording or reproducing apparatus, wherein the bearings for the staffs can be produced of inexpensive material, wherein such bearings can be rigidly connected to or made integral with their supports, which need not employ springs as a means for mounting the staffs, and which can stand rougher treatment and longer use than presently known coil assemblies.

A further object of the invention is to provide a novel frame, novel carriers for the bearings and novel holders for the pointer, balance weight and/or certain other parts of a coil assembly.

An additional object of the invention is to provide a coil as sembly wherein vibrations of the coil are damped more rapidly than in presently known coil assemblies.

The improved coil assembly comprises a preferably rectangular hollow frame having a first outer side and a second outer side located opposite the first outer side, a coil convoluted around the frame and overlying the two outer sides, a pair of elastic plastic carriers connected with the frame so that each thereof is outwardly adjacent to but normally spaced from one outer side of the frame and the corresponding portion of the coil, and a pair of coaxial pivot members or staffs each supported by one of the carriers and each extending outwardly from the respective carrier. Such pivot members are preferably anchored in bearing sleeves which form integral parts of the respective carriers.

It will be seen that the bearings for the pivot members may consist of the same relatively inexpensive (plastic) material as the carriers. Also, and in contrast to the construction of conventional coil assemblies, the bearings are preferably integral with the corresponding carriers. Since the carriers are elastic and are normally spaced from the adjoining portions of the coil, they can yield inwardly toward the corresponding outer sides of the frame even though the pivot members are not mounted on metallic springs. It was found that the elastic carriers effect more rapid damping of vibrations of the coil than the carriers for the pivot members of conventional coil assemblies. This renders it possible to utilize the improved coil assembly with particular advantage in moving-coil instruments which must be installed in tape recorders or analogous sound recording and/or reproducing apparatus. In such apparatus, the coil tends to vibrate at certain sound frequencies.

The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The improved coil assembly itself, however, both as to its construction and the mode of assembling the same, together with additional features and advantages thereof, will be best understood upon perusal of the following detailed description of certain specific embodiments with reference to the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is an exploded perspective view of certain component parts of a coil assembly which embodies the invention;

FIG. 2 is a plan view of a carrier, substantially as seen in the direction of arrow II in FIG. 1;

FIG. 3 is a transverse sectional view as seen in the direction of arrows from the line Ill-Ill of FIG. 2; and

FIG. 4 is a perspective view of a modified carrier.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 illustrates a substantially rectangular hollow frame 1 which constitutes one component part of a coil assembly for use in a moving-coil instrument, such as a galvanometer. This frame consists of metallic material and its longer walls la, 1b are respectively provided with outwardly extending male coupling portions 2, 3 and 4, 5 which comprise elongated ribs intending in parallelism with the planes of the respective walls 1a, 1b and receivable in grooves defined by complementary female coupling portions 8, 9 and 1 1 10 respectively provided on two platelike carriers l2, 13 consisting of elastic synthetic plastic material. The shorter walls 1c, 1d of the frame 1 are provided with outwardly extending projections in the form of elongated flanges 6, 7 and 6', 7'. The coupling portions 2-5 and flanges 6-7 define an elongated channel for and flank the convolutions of a coil 29 which is shown in FIG. 3.

The outer side of each of the two elastic carriers 12, 13 is provided with an integral bearing sleeve 14. When the carriers are properly attached to the frame 1, the axis of one of the sleeves 14 coincides with the axis of the other sleeve and these sleeves then extend outwardly from the respective carriers. Two pointed pivot members or staffs 15 are anchored in the sleeves 14 and serve as a means for turnably mounting the coil assembly in a moving-coil instrument in a manner well known from the art of such apparatus and forming no part of the present invention. The inner ends of the pivot members 15 do not extend beyond the inner sides of the respective carriers.

As shown in FIGS. 1 to 3, the outer side of the carrier 12 is connected with a platelike metallic or plastic holder 16 which serves as a support for certain additional component parts of the coil assembly. In the illustrated embodiment, the holder 16 is integral with a pointer 17 and with a balance weight 18. This holder comprises four cover portions or lugs each of which is provided with an opening or hole. These holes are shown in FIG. 2, as at 19, 19', 20 and 20'. The surfaces surrounding these holes taper inwardly, i.e., toward the outer side of the carrier 12 (see FIG. 3). During assembly, the holder 16 is placed onto the carrier 12 and the parts 12, 16 are then subjected to an ultrasonic treatment which causes the material of the carrier to flow into the holes 19, 19', 20, 20' so that, after its material hardens, the carrier 12 is permanently connected to the holder 16 at four points. A similar holder (not shown) is or may be connected to the other carrier 13 in the same way. Such second holder can support or comprise one or more additional parts of the coil assembly, for example, a terminal for connection of the customary torsion spring (not shown).

Each of the carriers l2, 13 is provided with two cutouts here shown as elongated slots 21, 22 and 23, 24. Each of these slots comprises an elongated central section and two end sections 25, 26 and 27, 28 (see the slots 21, 22 of the carrier 12 in FIG. 2). Each end section in the carrier 12 is adjacent to one corner portion of the holder 16. The central sections of the slots 21, 22 extend in parallelism with the respective coupling portions 2, 3 and 8, 9 and each such central section is located between one of the coupling portions 2, 3 and the corresponding pivot member 15. The end sections 25-28 are inclined with reference to and preferably make angles of degrees with the respective central sections. As shown in FIG. 2, the slots 21, 22 of the carrier 12 are formed in such a way that the comer portions of the holder 16 cannot engage those marginal portions of the carrier 12 which are outwardly adjacent to the end sections 25 28 when the pivot member 15 of FIG. 2 is caused to move toward the outer side of the wall In on the frame I. The slots 21, 22 and 23, 24 enhance the flexibility and elasticity of the carriers 12 and 13. FIG. 3 shows that the median portion of the carrier 12 is normally spaced from the adjoining portion of the coil 29, namely, from that portion of the coil which is adjacent to the outer side of the wall 1a. The gap between the coil 29 and the carrier 12 permits some inward movement of the carrier 12 and pivot member 15 (arrow a) so that the carrier can flex without touching the coil. A similar gap is provided between the inner side of the carrier 13 and that portion of the coil 29 which is adjacent to the outer side of the wall 112. These gaps are important and advantageous because the central portions of the carriers 12, 13 (between the central sections of the respective slots 21, 22 and 23, 24) can yield in a direction toward the walls In, lb without damage to the coil when the one or the other pivot member 15 is depressed in the direction indicated by arrow a. Since the holder 16 is connected to the carrier 12 at four points only, it can remain in a single plane (i.e., it remains flat) when the corresponding pivot member 15 is depressed in the direction indicated by arrow a. This is due to the fact that the four points of connection (holes 19, 19', 20, 20') are located at the four comers of the holder 16. It was further found that the carriers 12, 13 and/or holder 16 can damp vibrations of the coil 29 more rapidly than in conventional coil assemblies wherein the pivot members are mounted on metallic springs.

FIG. 4 illustrates a portion of a modified carrier 30. This carrier again consists of elastic synthetic plastic material but is reinforced by a springy element here shown as a metallic leaf spring 31. This leaf spring is a plate having notches 36, 37 and its four comer portions are connected to the carrier 30 (as at 32, 33, 34 and 35) in the same way as described for the carrier 12 and holder 16. The purpose of the leaf spring 31 is to insure that the central portion of the carrier 30 can return to its normal position after long periods of use and after being subjected to very high stresses which might cause fatigue of the material of the carrier. The leaf spring 31 is installed at the inner side of the carrier 30, namely, at that side which is adjacent to the outer side of the wall 1a or 1b. If desired, the spring 31 can be simply inserted between the frame 1 and the carrier 30 without being connected to the carrier. Such loosely mounted leaf spring is then placed between the coupling portions 2, 3, or 4, 5 and the complementary coupling portions of the corresponding carrier 30. Still further, the leaf spring 31 can be simply placed in requisite position against the inner side of the carrier 31 and is permanently connected to such carrier by plasticized material which is the same as the material of the carrier. The notches 36, 37 enhance the elasticity and flexibility of the leaf spring 31. These notches can be replaced by slots or the like.

The illustrated mode of connecting the leaf spring 31 to the carrier 30 is preferred at this time because the leaf spring can be connected to the carrier simultaneously with connection of the carrier 30 with a holder 16. Thus, each of the four points 32-35 shown in FIG. 4 is in registry with one of the four holes 19, 19', 20, 20' shown in FIG. 2. The leaf spring 31 is of particular advantage when the coil assembly is installed in a moving-coil instrument which is to be used in areas where the temperature is extremely high or extremely low so that the material of the carrier 30 is likely to exhibit fatigue.

The improved coil assembly is susceptible of many modifications without departing from the spirit of our invention. For example, the slots 21, 22 and/or 23, 24 can be omitted if the carrier 12 and/or 13 can be weakened (in order to become more elastic) in another way. Thus, it is possible to simply reduce the thickness of certain portions of the carriers to such an extent that the thus weakened portions contribute to greater flexibility and elasticity of the carriers.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features which fairly constitute essential characteristics of the generic and specific aspects of our contribution to the art.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims:

1. In a coil assembly for moving-coil instruments, a combination comprising a frame having a first outer side and a second outer side located opposite said first outer side; a coil convoluted around said frame and overlying said outer sides; a pair of elastic plastic carriers connected with said frame, each of said carriers being outwardly adjacent to one of said outer sides and each thereof being normally out of contact with the adjoining portion of said coil; and a pair of coaxial pivot members each supported by one of said carriers and each extending outwardly from the respective carrier, at least one of said pivot members being yieldable toward the other pivot member due to elasticity of the respective carrier.

2. A combination as defined in claim 1, wherein said frame comprises a first set of coupling portions flanking said outer sides thereof and said carriers comprise a second set of complementary coupling portions engaging with the respective first coupling portions.

3. A combination as defined in claim 1, wherein said carriers comprise weakened portions which enhance the elasticity of such carriers.

4. A combination as defined in claim 3, wherein said weakened portions are provided with cutouts.

5. A combination as defined in claim 4, wherein said cutouts are elongated slots.

6. A combination as defined in claim 5, wherein each of said carriers comprises a pair of substantially parallel coupling portions flanking the adjoining portion of said coil and connected with said frame, each of said slots being parallel with one of said coupling portions.

7. A combination as defined in claim 6, wherein each of said carriers is provided with two slots and wherein each of said slots is located between one of said coupling portions and the pivot member on the respective carrier.

8. A combination as defined in claim 5, wherein each of said slots comprises an elongated central section and two shorter end sections which are inclined with reference to said central section.

9. A combination as defined in claim 1, further comprising a substantially platelike holder outwardly adjacent and secured to at least one of said carriers.

10. A combination as defined in claim 9, further comprising a pointer provided on said holder.

11. A combination as defined in claim 9, wherein said holder is secured to said one carrier at a plurality of points.

12. A combination as defined in claim 11, wherein said holder comprises a plurality of comer portions and wherein said one carrier is provided with a plurality of slots each having end sections, each of said end sections being adjacent to one of said comer portions.

13. A combination as defined in claim 1, wherein each of said carriers comprises an integral sleeve and wherein said pivot members are anchored in the respective sleeves.

14. In a coil assembly for moving-coil instruments, a combination comprising a frame having a first outer side and a second outer side located opposite said first outer side, said frame comprising a first set of coupling portions flanking said outer sides thereof; a coil convoluted around said frame and overlying said outer sides; a pair of elastic plastic carriers connected with said frame, each of said carriers being outwardly adjacent to one of said outer sides and each thereof being normally out of contact with the adjoining portion of said coil, said carriers comprising a second set of complementary coupling portions engaging with the respective first coupling portions, one set of said coupling portions being provided with elongated grooves and the other set of said coupling portions comprising elongated ribs removably received in said grooves; and a pair of coaxial pivot members each supported by one of said carriers and each extending outwardly from the respective carrier.

15. In a coil assembly for moving-coil instruments, a combination comprising a frame having a first outer side and a second outer side located opposite said first outer side; a coil convoluted around said frame and overlying said outer sides; a pair of elastic plastic carriers connected with said frame, each of said carriers being outwardly adjacent to one of said outer sides and each thereof being normally out of contact with the adjoining portion of said coil; a springy reinforcing element for each of said carriers; and a pair of coaxial pivot members each supported by one of said carriers and each extending outwardly from the respective carrier.

16. A combination as defined in claim 15, wherein each of said reinforcing elements is a metallic leaf spring.

17. A combination as defined said reinforcing elements is conn er at a plurality of points.

in claim 15, wherein each of ected to the respective carri- 

1. In a coil assembly for moving-coil instruments, a combination comprising a frame having a first outer side and a second outer side located opposite said first outer side; a coil convoluted around said frame and overlying said outer sides; a pair of elastic plastic carriers connected with said frame, each of said carriers being outwardly adjacent to one of said outer sides and each thereof being normally out of contact with the adjoining portion of said coil; and a pair of coaxial pivot members each supported by one of said carriers and each extending outwardly from the respective carrier, at least one of said pivot members being yieldable toward the other pivot member due to elasticity of the respective carrier.
 2. A combination as defined in claim 1, wherein said frame comprises a first set of coupling portions flanking said outer sides thereof and said carriers comprise a second set of complementary coupling portions engaging with the respective first coupling portions.
 3. A combination as defined in claim 1, wherein said carriers comprise weakened portions which enhance the elasticity of such carriers.
 4. A combination as defined in claim 3, wherein said weakened portions are provided with cutouts.
 5. A combination as defined in claim 4, wherein said cutouts are elongated slots.
 6. A combination as defined in claim 5, wherein each of said carriers comprises a pair of substantially parallel coupling portions flanking the adjoining portion of said coil and connected with said frame, each of said slots being parallel with one of said coupling portions.
 7. A combination as defined in claim 6, wherein each of said carriers is provided with two slots and wherein each of said slots is located between one of said coupling portions and the pivot member on the respective carrier.
 8. A combination as defined in claim 5, wherein each of said slots comprises an elongated central section and two shorter end sections which are inclined with reference to said central section.
 9. A combination as defined in claim 1, further comprising a substantially platelike holder outwardly adjacent and secured to at least one of said carriers.
 10. A combinatioN as defined in claim 9, further comprising a pointer provided on said holder.
 11. A combination as defined in claim 9, wherein said holder is secured to said one carrier at a plurality of points.
 12. A combination as defined in claim 11, wherein said holder comprises a plurality of corner portions and wherein said one carrier is provided with a plurality of slots each having end sections, each of said end sections being adjacent to one of said corner portions.
 13. A combination as defined in claim 1, wherein each of said carriers comprises an integral sleeve and wherein said pivot members are anchored in the respective sleeves.
 14. In a coil assembly for moving-coil instruments, a combination comprising a frame having a first outer side and a second outer side located opposite said first outer side, said frame comprising a first set of coupling portions flanking said outer sides thereof; a coil convoluted around said frame and overlying said outer sides; a pair of elastic plastic carriers connected with said frame, each of said carriers being outwardly adjacent to one of said outer sides and each thereof being normally out of contact with the adjoining portion of said coil, said carriers comprising a second set of complementary coupling portions engaging with the respective first coupling portions, one set of said coupling portions being provided with elongated grooves and the other set of said coupling portions comprising elongated ribs removably received in said grooves; and a pair of coaxial pivot members each supported by one of said carriers and each extending outwardly from the respective carrier.
 15. In a coil assembly for moving-coil instruments, a combination comprising a frame having a first outer side and a second outer side located opposite said first outer side; a coil convoluted around said frame and overlying said outer sides; a pair of elastic plastic carriers connected with said frame, each of said carriers being outwardly adjacent to one of said outer sides and each thereof being normally out of contact with the adjoining portion of said coil; a springy reinforcing element for each of said carriers; and a pair of coaxial pivot members each supported by one of said carriers and each extending outwardly from the respective carrier.
 16. A combination as defined in claim 15, wherein each of said reinforcing elements is a metallic leaf spring.
 17. A combination as defined in claim 15, wherein each of said reinforcing elements is connected to the respective carrier at a plurality of points.
 18. A combination as defined in claim 15, wherein each of said reinforcing elements is a notched plate. 